Abstract
We previously researched whisker growth from solder, and reported that whiskers occurred from a non-corroded tin layer that was sandwiched between the non-uniform progressed corroded tin layers in a high-temperature and high-humidity atmosphere.
Here, we report further on the results obtained from the EPMA analysis and the electrochemical properties. First, it was ascertained that the corrosion of tin was promoted as bromine in the flux invaded the solder. Furthermore, in addition to the high-temperature and high-humidity environment, oxygen was found to be indispensable for the generation of whiskers, and to finally change into tin oxide through tin hydroxide.
In addition, from an experiment that varied the temperature while maintaining a uniform relative humidity, it is understood that the activation energy was 0.84 eV when whiskers were generated from the solder. Also, an experiment that changed the relative humidity while maintaining a uniform temperature revealed that a plot of the whisker-generating time forms a straight line on a semi-log plot for the reciprocal number of the relative humidity.
